The proposed research is concerned with the postnatal development of the visual system in the cat. Anatomical methods involving light and electron microscopy will be employed to study: a. the formation of synaptic relations in the lateral geniculate nucleus; b. the development of the geniculo-cortical pathway in normal and deprived cats; c. the reorganization of retino-geniculate, retino-tectal, and geniculo-cortical pathways following neonatal lesions of visual cortex; and d. the effects of strabismus on cell size in the lateral geniculate and on the distribution of geniculo-cortical afferents. In addition, behavioral methods will be used to study visual acuity in strabismic cats, and to investigate the role of binocular interaction in the development of perceptual deficits.